Just like the RADIUS protocol, we often use TACACS+ within the AAA framework in order to communicate between the authenticator and the authentication server.

Unlike RADIUS, TACACS+ is a Cisco proprietary protocol. It is based on an earlier TACACS protocol, and is not compatible with the preceding TACACS or XTACACS protocols.

Another unique aspect of TACACS+ when compared to RADIUS is modularity. TACACS+ allows the implementation of authentication, authorization, and accounting independently of each other.
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In the process of writing the article series about the DHCP Snooping, I realized that DHCP Relays are a subject that is often misunderstood by network engineers. The aim of this article, which we can say is an appendix to the “Understanding DHCP Snooping” series is to explore the functionality of DHCP Relays, as implemented by Cisco IOS.
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The following is an excerpt from the upcoming IPexpert book – IPv4/IPv6 QoS Operation and Troubleshooting

One of the points that many Cisco QoS texts fail to make clear is that a typical Cisco network device interface possess a software queue and a hardware queue for outbound traffic transmissions. When we read that a particular QoS tool will engage and work in times of congestion only, this is a reference to packets overflowing the hardware queue into the software queue. The software queue is where the magic of Quality of Service happens. In fact, one of the QoS mechanisms called Link Fragmentation and Interleaving (LFI) directly addresses the split between these two queues. LFI ensures that large packets (Jumbograms) do not clog the hardware queue. These large packets are chopped up (fragmented) so that higher priority, smaller packets (like voice) can be interwoven between the fragments in the hardware queue. Chapter 11: Link Fragmentation and Interleaving (LFI) details this process for you.
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RADIUS is an important protocol for Authentication, Authorization, and Accounting functionality in many networks today. RADIUS is a complete open standard. The security protocol was detailed in RFCs 2865 and 2866.

RADIUS operates in a client/server fashion. A Cisco device, such as a router or a firewall, acts as the client. This device sends a request to an authentication server, such as a Cisco Access Control Server (ACS), that acts as the server. The ACS box contains all the user account information, or this box links to a datastore like Active Directory.
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While I enjoy working on complex issues, sometimes they are best explored in simpler environments. We don’t need dozens of switches and routes to learn how things work. With this in mind, I will expand our original network with a single switch and router.
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